Light emitting element and display device

ABSTRACT

A light emitting element and display device are disclosed. In one example, a light emitting element includes a first electrode formed on a base body. A first insulation layer is formed on the base body and the first electrode and has an aperture portion in which a part of the first electrode is exposed. A second insulation layer is formed on the first insulation layer and has a protruding end portion protruding from the aperture portion. A third insulation layer is formed on the second insulation layer and has an end portion recessed from the protruding end portion. A charge injection/transport layer is formed over the second insulation layer and the third insulation layer. An organic layer includes a light emitting layer, and a second electrode formed on the organic layer. At least a part of the charge injection/transport layer is discontinuous at the protruding end portion.

TECHNICAL FIELD

The present disclosure relates to a light emitting element and a displaydevice.

BACKGROUND ART

In recent years, as a display device substituted for a liquid crystaldisplay device, an organic electroluminescence display device(hereinafter, also simply abbreviated as an “organic EL display device”)using an organic electroluminescence element (hereinafter, also simplyabbreviated as an “organic EL element”) has attracted attention. Theorganic EL display device is a self-luminous type, has a characteristicof low power consumption, and is considered to have sufficientresponsiveness even to a high-definition high-speed video signal.Development and commercialization of the organic EL display device forpractical use are keenly proceeding.

In the organic EL display device, high contrast and high colorreproducibility can be realized, for example, by constituting one pixelwith three sub-pixels (light emitting elements) constituted by asub-pixel having a red light emitting layer and constituted by a lightemitting element that emits red light, a sub-pixel having a green lightemitting layer and constituted by a light emitting element that emitsgreen light, and a sub-pixel having a blue light emitting layer andconstituted by a light emitting element that emits blue light.Meanwhile, reduction of a pixel pitch is required for high resolution.However, it becomes more difficult to constitute one pixel with suchthree sub-pixels as the pixel pitch becomes finer.

Therefore, development of a method for forming a white light emittinglayer over all pixels and coloring white light using a color filter,that is, development of technology for constituting one pixel with threesub-pixels of a red sub-pixel (referred to as a “red light emittingelement”) obtained by combining a light emitting element having a whitelight emitting layer (referred to as a “white light emitting element”)and a red color filter, a green sub-pixel (referred to as a “green lightemitting element”) obtained by combining a white light emitting elementand a green color filter, and a blue sub-pixel (referred to as a “bluelight emitting element”) obtained by combining a white light emittingelement and a blue color filter is proceeding. The white light emittinglayer is formed as a continuous layer over the entire white lightemitting element. It is unnecessary to form the red light emittinglayer, the green light emitting layer, and the blue light emitting layerfor each sub-pixel. Therefore, the pixel pitch can be fine. In eachwhite light emitting element, the white light emitting layer is formedbetween a first electrode and a second electrode. The first electrode isformed independently in each light emitting element. Meanwhile, thesecond electrode is common in each light emitting element.

In such a configuration, a phenomenon that a leakage current flowsbetween a first electrode of a certain light emitting element and asecond electrode constituting a light emitting element (referred to asan “adjacent light emitting element” for convenience) adjacent to thecertain light emitting element may occur. In addition, when such aphenomenon occurs, light emission occurs in a light emitting elementwhich should not emit light originally. Meanwhile, a current in a lightemitting element which should emit light is reduced. As a result,blurring occurs in an image, and the chromaticity of the entire pixelsmay be shifted from desired chromaticity disadvantageously.

A means for solving such a problem is known, for example, from JapanesePatent Application Laid-open No. 2014-232631. A display device disclosedin this patent publication includes, successively from a substrate side,a plurality of first electrodes each formed in each pixel, and aperturesrespectively opposed to the plurality of first electrodes. The displaydevice further includes an insulation layer having covers on edgeportions of the apertures, a charge injection/transport layer which iscut at the covers of the insulation layer or the resistance of which isincreased and indicating at least one of a charge injection property anda charge transport property, an organic layer including one or morelight emitting layers common in all the pixels, and a second electrodeformed over the entire surface of the organic layer.

CITATION LIST Patent Document Patent Document 1: Japanese PatentApplication Laid-Open No. 2014-232631 SUMMARY OF THE INVENTION Problemsto be Solved by the Invention

As described above, in the display device disclosed in the above patentpublication, the charge injection/transport layer is cut at covers ofthe insulation layer or the resistance thereof is increased, andtherefore a phenomenon that a leakage current flows between a firstelectrode of a certain light emitting element and a second electrodeconstituting an adjacent light emitting element hardly occurs. However,in some cases, even in such a configuration, prevention of generation ofa leakage current may be insufficient.

Therefore, an object of the present disclosure is to provide a lightemitting element having a configuration and a structure in which aphenomenon that a leakage current flows between a first electrode in acertain light emitting element and a second electrode constituting anadjacent light emitting element hardly occurs, and a display deviceconstituted by the light emitting element.

Solutions to Problems

The light emitting element of the present disclosure for achieving theabove object includes:

a first electrode formed on a base body;

a first insulation layer formed on the base body and the first electrodeand having an aperture portion in which a part of the first electrode isexposed;

a second insulation layer formed on the first insulation layer andhaving a protruding end portion protruding from the aperture portiondisposed in the first insulation layer;

a third insulation layer formed on the second insulation layer andhaving an end portion recessed from the protruding end portion of thesecond insulation layer;

a charge injection/transport layer formed over the second insulationlayer and the third insulation layer from the first electrode;

an organic layer formed on the charge injection/transport layer andincluding a light emitting layer formed of an organic light emittingmaterial; and

a second electrode formed on the organic layer, and

at least apart of the charge injection/transport layer is discontinuousat the protruding end portion of the second insulation layer.

In order to achieve the above object, the display device of the presentdisclosure is formed of a plurality of the above light emitting elementsof the present disclosure arranged in a two-dimensional matrix.

Effects of the Invention

In the light emitting element of the present disclosure or a lightemitting element constituting the display device of the presentdisclosure (hereinafter, these light emitting elements are collectivelyreferred to as a “light emitting element or the like of the presentdisclosure” for convenience), the protruding end portion protruding fromthe aperture portion (that is, the protruding end portion protrudingfrom the first insulation layer and the third insulation layer) isdisposed in the second insulation layer sandwiched by the firstinsulation layer and the third insulation layer. Therefore, at least apart of the charge injection/transport layer formed over the secondinsulation layer and the third insulation layer from the first electrodeis reliably discontinuous at the protruding end portion. That is, thecharge injection/transport layer is reliably cut at the protruding endportion of the second insulation layer or the resistance thereof isincreased, and therefore occurrence of a phenomenon that a leakagecurrent flows between a first electrode of a certain light emittingelement and a second electrode constituting an adjacent light emittingelement can be reliably prevented. Note that effects described hereinare merely illustrative, and are not restrictive. In addition, anadditional effect may be present.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic partial cross-sectional view of a display deviceof a first embodiment.

FIG. 2 is an enlarged schematic partial cross-sectional view of a firstinsulation layer, a second insulation layer, a third insulation layer,and the like in a light emitting element constituting the display deviceof the first embodiment.

FIG. 3 is an enlarged schematic partial cross-sectional view of anorganic layer and the like in the light emitting element constitutingthe display device of the first embodiment.

FIG. 4 is a schematic partial cross-sectional view illustrating aninterlayer insulation layer and the like for describing a method formanufacturing the display device of the first embodiment.

FIG. 5 is a schematic partial cross-sectional view illustrating aninterlayer insulation layer and the like for describing the method formanufacturing the display device of the first embodiment, following FIG.4.

FIG. 6 is a schematic partial cross-sectional view illustrating aninterlayer insulation layer and the like for describing the method formanufacturing the display device of the first embodiment, following FIG.5.

FIG. 7 is a schematic partial cross-sectional view illustrating aninterlayer insulation layer and the like for describing the method formanufacturing the display device of the first embodiment, following FIG.6.

FIG. 8 is a schematic partial cross-sectional view illustrating aninterlayer insulation layer and the like for describing a method formanufacturing a display device of a second embodiment.

FIG. 9 is a schematic partial cross-sectional view illustrating aninterlayer insulation layer and the like for describing the method formanufacturing the display device of the second embodiment, followingFIG. 8.

FIG. 10 is a schematic partial cross-sectional view illustrating aninterlayer insulation layer and the like for describing the method formanufacturing the display device of the second embodiment, followingFIG. 9.

FIG. 11 is a cross-sectional photograph of a first electrode and thelike constituting a light emitting element in a process of manufacturingthe display device of the second embodiment.

FIGS. 12A and 12B are diagrams illustrating simulation results of anelectric field concentration state in a case where a top surface of thepart of an organic layer positioned above a region beyond the thirdinsulation layer from the protruding end portion of the secondinsulation layer is not gentle and in a case where the top surface isgentle, respectively.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present disclosure will be described on the basis ofembodiments with reference to the drawings. However, the presentdisclosure is not limited to the embodiments, but various numericalvalues and materials in the embodiments are illustrative. Note thatdescription will be made in the following order.

1. General description on light emitting element of the presentdisclosure and display device of the present disclosure

2. First embodiment (light emitting element of the present disclosureand display device of the present disclosure)

3. Second embodiment (modification of the first embodiment)

4. Others

<General Description on Light Emitting Element of the Present Disclosureand Display Device of the Present Disclosure>

In a light emitting element or the like of the present disclosure, a topsurface of each of a second insulation layer and a third insulationlayer in a region beyond the third insulation layer from a protrudingend portion of the second insulation layer can be gentle. As a result,an organic layer and a second electrode formed thereon also becomegentle, and concentration of an electric field formed by a firstelectrode and a second electrode in a light emitting layer can besuppressed. When electric field concentration occurs in the lightemitting layer, there is a possibility that a light emitting state inthe light emitting layer becomes nonuniform. Alternatively, for example,a phenomenon that a region of the light emitting layer corresponding toan edge portion of an aperture emits light in a ring shape (frame shape)occurs. The phrase “a top surface of each of a second insulation layerand a third insulation layer is gentle” means that a curve of a topsurface of each of the second insulation layer and the third insulationlayer, obtained by cutting the second insulation layer and the thirdinsulation layer along a virtual vertical surface passing through acenter of the light emitting element can be differentiated. Note that apart of the curve of the top surface may include a region that cannot bedifferentiated.

In the light emitting element or the like of the present disclosureincluding the above preferred form, a material constituting the firstinsulation layer, a material constituting the second insulation layer,and a material constituting the third insulation layer can be differentfrom one another. Specifically, the insulation layers are preferablyconstituted by a material in which the second insulation layer and thethird insulation layer are hardly etched when the first insulation layeris etched, a material in which the first insulation layer and the thirdinsulation layer are hardly etched when the second insulation layer isetched, and a material in which the first insulation layer and thesecond insulation layer are hardly etched when the third insulationlayer is etched. Examples of a combination of (a material constitutingthe first insulation layer, a material constituting the secondinsulation layer, and a material constituting the third insulationlayer) include (an SiN-based material, an SiC-based material, and anSiO₂-based material), (an SiN-based material, an SiO₂-based material,and an SiC-based material), (an SiC-based material, an SiN-basedmaterial, and an SiO₂-based material), (an SiC-based material, anSiO₂-based material, and an SiN-based material), (an SiO₂-basedmaterial, an SiN-based material, and an SiC-based material), and (anSiO₂-based material, an SiC-based material, and an SiN-based material).Herein, the SiN-based material also includes SiON. This also applies tothe following. Alternatively, in the light emitting element or the likeof the present disclosure including the above preferred forms, amaterial constituting the first insulation layer can be different from amaterial constituting the second insulation layer and a materialconstituting the third insulation layer, and the material constitutingthe second insulation layer and the material constituting the thirdinsulation layer can be the same as each other. Specifically, theinsulation layers are preferably constituted by a material in which thesecond insulation layer and the third insulation layer are hardly etchedwhen the first insulation layer is etched, and a material in which thefirst insulation layer is hardly etched when the second insulation layerand the third insulation layer are etched. Examples of a combination of(a material constituting the first insulation layer and a materialconstituting each of the second insulation layer and the thirdinsulation layer) include (an SiN-based material and an SiC-basedmaterial), (an SiC-based material and an SiN-based material), (anSiN-based material and an SiO₂-based material), (an SiO₂-based materialand an SiN-based material), (an SiC-based material and an SiO₂-basedmaterial), and (an SiO₂-based material and an SiC-based material). Whena certain insulation layer is etched, in a case where another insulationlayer is hardly etched, it is said that there is a large etchingselection ratio between the certain insulation layer and the otherinsulation layer. Here, the etching selection ratio may be two or morealthough being not limited thereto.

Furthermore, in the light emitting element or the like of the presentdisclosure including the above-described preferred forms andconfigurations, the resistance of the charge injection/transport layercan be increased due to discontinuity in at least a part of the chargeinjection/transport layer at the protruding end portion of the secondinsulation layer. The entire charge injection/transport layer may bediscontinuous at the protruding end portion of the second insulationlayer. Alternatively, as long as the state is sufficiently highlyresistant, the charge injection/transport layer may be partiallyconnected or may be connected with an extremely thin thickness.

Furthermore, in the light emitting element or the like of the presentdisclosure including the above-described preferred forms andconfigurations, the thickness of the second insulation layer above thefirst electrode can be smaller than the thickness of each of the firstinsulation layer and the third insulation layer above the firstelectrode. As a result, at least a part of the chargeinjection/transport layer can be reliably discontinuous at theprotruding end portion of the second insulation layer, and theresistance of the charge injection/transport layer can be increased morereliably. A thickness T₂ of the second insulation layer above the firstelectrode may be 3 nm to 30 nm, for example. A thickness T₁ of the firstinsulation layer above the first electrode may be 5 nm to 50 nm, forexample. A thickness T₃ of the third insulation layer above the firstelectrode may be 5 nm to 50 nm, for example. Alternatively, thefollowing can be exemplified.

0.06≤T ₂ /T ₁≤6

0.06≤T ₂ /T ₃≤6

0.1≤T ₃ /T ₁≤10

A length L₂ of the protruding end portion of the second insulation layerprotruding from the aperture portion may be 10 nm to 150 nm, forexample. A relation (aspect ratio) between the length L₂ of theprotruding end portion of the second insulation layer and the thicknessT₁ of the first insulation layer may be 0.5≤L₂/T₁≤30, for example. As arelation between a projection image of an edge portion of an apertureportion in the first insulation layer on the first electrode (referredto as an “aperture portion edge portion projection image”) and aprojection image of an edge portion of the third insulation layer on thefirst electrode (referred to as a “third insulation layer edge portionprojection image”), the aperture portion edge portion projection imagemay overlap the third insulation layer edge portion projection image,the aperture portion edge portion projection image may be included inthe third insulation layer edge portion projection image, or the thirdinsulation layer edge portion projection image may be included in theaperture portion edge portion projection image. Examples of a planarshape of the aperture portion include a square shape, a square shapewith four corners rounded, a rectangular shape, a rectangular shape withfour corners rounded, a circular shape, and an elliptical shape.

Furthermore, in the light emitting element or the like of the presentdisclosure including the above-described preferred forms andconfigurations, the light emitting layer may be constituted by at leasttwo light emitting layers that emit different colors. In this case,light emitted from the organic layer may be white. Specifically, thelight emitting layer may have a structure obtained by laminating threelayers of a red light emitting layer that emits red light (wavelength:620 nm to 750 nm), a green light emitting layer that emits green light(wavelength: 495 nm to 570 nm), and a blue light emitting layer thatemits blue light (wavelength: 450 nm to 495 nm), and emits white lightas a whole. Alternatively, the light emitting layer may have a structureobtained by laminating two layers of a blue light emitting layer thatemits blue light and a yellow light emitting layer that emits yellowlight, and emits white light as a whole. Alternatively, the lightemitting layer may have a structure obtained by laminating two layers ofa blue light emitting layer that emits blue light and an orange lightemitting layer that emits orange light, and emits white light as awhole. In addition, such a white light emitting element that emits whitelight includes a red color filter to constitute a red light emittingelement. The white light emitting element includes a green color filterto constitute a green light emitting element. The white light emittingelement includes a blue color filter to constitute a blue light emittingelement. One pixel is constituted by a red light emitting element, agreen light emitting element, and a blue light emitting element. In somecases, one pixel may be constituted by a red light emitting element, agreen light emitting element, a blue light emitting element, and a lightemitting element that emits white light (or a light emitting elementthat emits complementary color light). Note that, in a form constitutedby at least two light emitting layers that emit light of differentcolors, there is actually a case where the light emitting layers thatemit light of different colors are mixed and are not clearly separatedinto the layers. Alternatively, one pixel may be constituted by threesub-pixels (light emitting elements) of a sub-pixel having a red lightemitting layer and constituted by a light emitting element that emitsred light, a sub-pixel having a green light emitting layer andconstituted by a light emitting element that emits green light, and asub-pixel having a blue light emitting layer and constituted by a lightemitting element that emits blue light. Alternatively, one pixel may beconstituted by four sub-pixels (light emitting elements) of a sub-pixelhaving a red light emitting layer and constituted by a light emittingelement that emits red light, a sub-pixel having a green light emittinglayer and constituted by a light emitting element that emits greenlight, a sub-pixel having a blue light emitting layer and constituted bya light emitting element that emits blue light, and a sub-pixelincluding alight emitting element that emits white light (or a lightemitting element that emits complementary color light).

The color filter is constituted by a resin to which a coloring agentcontaining a desired pigment or dye is added. By selecting a pigment ora dye, adjustment is performed such that light transmittance in a targetwavelength range of red, green, blue, or the like is high, and lighttransmittance in the other wavelength ranges is low. For a lightemitting element that emits white light, it is only required to disposea transparent filter. A black matrix layer (light shielding layer) maybe formed between a color filter and a color filter. For example, theblack matrix layer is constituted by a black resin film (specifically,made of a black polyimide resin, for example) having an optical densityof 1 or more, mixed with a black coloring agent, or a thin film filterusing interference of a thin film. The thin film filter is formed bylaminating two or more thin films made of metal, metal nitride, or metaloxide, for example, and attenuates light by utilizing interference of athin film. Specific examples of the thin film filter include a thin filmfilter obtained by alternately laminating Cr and chromium (III) oxide(Cr₂O₃).

Furthermore, in the light emitting element or the like of the presentdisclosure including the above-described preferred forms andconfigurations, the charge injection/transport layer may exhibit atleast one of a charge injection property and a charge transportproperty. In a case where the first electrode is an anode electrode andthe second electrode is a cathode electrode, specifically, the chargeinjection/transport layer may be constituted by a hole injection layer.In a case where the hole injection layer is not formed but a holetransport layer is formed, the charge injection/transport layer may beconstituted by the hole transport layer.

Furthermore, in the light emitting element or the like of the presentdisclosure including the above-described preferred forms andconfigurations, the base body may be formed of a silicon semiconductorsubstrate on which a transistor (specifically, for example, a MOSFET) isformed and an interlayer insulation layer formed thereon, the firstelectrode and the first insulation layer may be formed on the interlayerinsulation layer, and the first electrode may be connected to thetransistor formed on the silicon semiconductor substrate via a contacthole formed in the interlayer insulation layer, although being notlimited thereto. Note that a display device having such a form isconstituted by a top emission type display device described below.

Furthermore, in the display device of the present disclosure includingthe light emitting element of the present disclosure including theabove-described preferred forms and configurations, the first insulationlayer, the second insulation layer, the third insulation layer, thecharge injection/transport layer, the organic layer, and the secondelectrode may be common in a plurality of light emitting elements.

The display device of the present disclosure including theabove-described various preferred forms may be constituted by an organicelectroluminescence display device (organic EL display device). Thelight emitting element of the present disclosure including theabove-described various preferred forms may be constituted by an organicelectroluminescence element (organic EL element)

In another expression, the display device of the present disclosureincludes a first substrate, a second substrate, and an image displayunit sandwiched by the first substrate and the second substrate. In theimage display unit, a plurality of the light emitting elements of thepresent disclosure including the above-described preferred forms andconfigurations is arranged in a two-dimensional matrix. Herein, thelight emitting elements are formed on a side of the first substrate.

The display device of the present disclosure may be a top emission typedisplay device that emits light from the second substrate or a bottomemission type display device that emits light from the first substrate.In the top emission type display device, it is only required to formacolor filter and a black matrix layer on a surface side of the secondsubstrate opposed to the first substrate. Meanwhile, in the bottomemission type display device, it is only required to form a color filterand a black matrix layer on a surface side of the first substrateopposed to the second substrate. As described above, in a case where thebase body is constituted by a silicon semiconductor substrate on which atransistor is formed and an interlayer insulation layer formed thereon,the silicon semiconductor substrate corresponds to the first substrate.Hereinafter, description will be made exclusively on the basis of anexample in which the display device is constituted by a top emissiontype display device. However, in a case where the display device isconstituted by a bottom emission type display device, the followingdescription is only required to be replaced appropriately.

In addition to the silicon semiconductor substrate, the first substrateor the second substrate may be formed of a high strain point glasssubstrate, a soda glass (Na₂O.CaO.SiO₂) substrate, a borosilicate glass(Na₂O.B₂O₃.SiO₂) substrate, a forsterite (2MgO.(SiO₂) substrate, a leadglass (Na₂O.PbO.SiO₂) substrate, various glass substrates each having aninsulating film formed on a surface thereof, a quartz substrate, aquartz substrate having an insulating film formed on a surface thereof,or an organic polymer such as polymethyl methacrylate (PMMA), polyvinylalcohol (PVA), polyvinyl phenol (PVP), polyether sulfone (PES),polyimide, polycarbonate, or polyethylene terephthalate (PET) (having aform of a polymer material such as a plastic film, a plastic sheet, or aplastic substrate constituted by a polymer material and havingflexibility). Materials constituting the first substrate and the secondsubstrate may be the same as or different from each other. However, inthe top emission type display device, the second substrate is requiredto be transparent to light from the light emitting element. In thebottom emission type display device, the first substrate is required tobe transparent to light from the light emitting element.

In a case where the first electrode is caused to function as an anodeelectrode, examples of a material constituting the first electrodeinclude aluminum (Al) and an alloy containing aluminum, and a metal suchas platinum (Pt), gold (Au), silver (Ag), chromium (Cr), molybdenum(Mo), titanium (Ti), tungsten (W), nickel (Ni), copper (Cu), iron (Fe),cobalt (Co), or tantalum (Ta) or an alloy thereof (for example, anAg—Pd—Cu alloy containing silver as a main component and containing 0.3%by mass to 1% by mass of palladium (Pd) and 0.3% by mass to 1% by massof copper (Cu), an Al—Nd alloy, or Al—Ni alloy). The thickness of thefirst electrode may be 0.1 μm to 1 μm, for example. Alternatively, thematerial constituting the first electrode may be a transparentconductive material having excellent hole injection characteristics,such as an oxide of indium and tin (ITO) or an oxide of indium and zinc(IZO), or may have a structure obtained by laminating a transparentconductive material having excellent hole injection characteristics,such as an oxide of indium and tin (ITO) or an oxide of indium and zinc(IZO) on a dielectric multilayer film or a reflective film having highlight reflectivity, formed of aluminum (Al) or the like. Meanwhile, in acase where the first electrode is caused to function as a cathodeelectrode, the first electrode is desirably constituted by a conductivematerial having a small work function value and high light reflectivity.However, by improving an electron injection property, for example, bydisposing an appropriate electron injection layer in a conductivematerial having high light reflectivity used as an anode electrode, theresulting conductive material can also be used as a cathode electrode.

Meanwhile, in a case where the second electrode is caused to function asa cathode electrode, a material constituting the second electrode (asemi-light transmitting material or a light transmitting material) isdesirably constituted by a conductive material having a small workfunction value so as to be able to transmit emitted light and inject anelectron into an organic layer efficiently. Examples of the materialconstituting the second electrode include a metal having a small workfunction and an alloy thereof, such as aluminum (Al), silver (Ag),magnesium (Mg), calcium (Ca), sodium (Na), strontium (Sr), an alkalimetal or an alkaline earth metal and silver (Ag) [for example, an alloyof magnesium (Mg) and silver (Ag) (Mg—Ag alloy)], an alloy ofmagnesium-calcium (Mg—Ca alloy), or an alloy of aluminum (Al) andlithium (Li) (Al—Li alloy). Among these materials, an Mg—Ag alloy ispreferable, and a volume ratio between magnesium and silver may beMg:Ag=5:1 to 30:1, for example. Alternatively, as a volume ratio betweenmagnesium and calcium may be Mg:Ca=2:1 to 10:1, for example. Thethickness of the second electrode may be 4 nm to 50 nm, preferably 4 nmto 20 nm, and more preferably 6 nm to 12 nm, for example. Alternatively,the second electrode may have a lamination structure of the abovematerial layer and a so-called transparent electrode (for example,thickness 3×10⁻⁸ m to 1×10⁻⁶ m) formed of, for example, ITO or IZO. Abus electrode (auxiliary electrode) formed of a low resistance materialsuch as aluminum, an aluminum alloy, silver, a silver alloy, copper, acopper alloy, gold, or a gold alloy may be disposed in the secondelectrode to reduce resistance as the whole second electrode. Meanwhile,in a case where the second electrode is caused to function as an anodeelectrode, the second electrode is desirably constituted by a conductivematerial that transmits emitted light and has a large work functionvalue. Average light transmittance of the second electrode is 50% to90%, and preferably 60% to 90%.

Examples of a method for forming the first electrode or the secondelectrode include a combination of a vapor deposition method includingan electron beam vapor deposition method, a hot filament vapordeposition method, and a vacuum vapor deposition method, a sputteringmethod, a chemical vapor deposition method (CVD method), an MOCVDmethod, and an ion plating method with an etching method; variousprinting methods such as a screen printing method, an inkjet printingmethod, and a metal mask printing method; a plating method (anelectroplating method or an electroless plating method); a lift-offmethod; a laser ablation method; and a sol-gel method. According tovarious printing methods and a plating method, the first electrode orthe second electrode having a desired shape (pattern) can be formeddirectly. Note that, in a case where the second electrode is formedafter the organic layer is formed, the second electrode is preferablyformed particularly on the basis of a film formation method in whichenergy of film formation particles is small, such as a vacuum vapordeposition method, or a film formation method such as an MOCVD methodfrom a viewpoint of preventing the organic layer from being damaged.When the organic layer is damaged, non-light emitting pixels (ornon-light emitting sub-pixels) called “dark spots” due to generation ofa leak current may be generated. In addition, processes from formationof the organic layer to formation of these electrodes are preferablyperformed without exposure thereof to the atmosphere from a viewpoint ofpreventing deterioration of the organic layer due to moisture in theatmosphere. As described above, in some cases, the second electrode doesnot need to be patterned, and may be a so-called common electrode.

The organic layer includes a light emitting layer. In addition to thelight emitting layer, for example, the organic layer may be constitutedby a lamination structure of a hole transport layer, a light emittinglayer, and an electron transport layer or a laminated structure of ahole transport layer and a light emitting layer serving also as anelectron transport layer. Examples of a method for forming the organiclayer include a physical vapor deposition method (PVD method) such as avacuum vapor deposition method; a printing method such as a screenprinting method or an inkjet printing method; a laser transfer method inwhich an organic layer on a laser absorption layer is separated byirradiating a lamination structure of a laser absorption layer and anorganic layer formed on a transfer substrate with a laser and theorganic layer is transferred, and various coating methods. In a casewhere the organic layer is formed on the basis of the vacuum vapordeposition method, for example, using a so-called metal mask, theorganic layer can be obtained by depositing a material that has passedthrough an aperture disposed in the metal mask, or the organic layer maybe formed on the entire surface without patterning as described above.In some cases, at least a part of a part of the organic layer(specifically, for example, a hole transport layer) may be discontinuousat a protruding end portion of the second insulation layer. Examples ofa method for forming the charge injection/transport layer include a PVDmethod such as a vacuum vapor deposition method.

The thickness of a hole transport layer (hole supply layer) and thethickness of an electron transport layer (electron supply layer) arepreferably substantially equal to each other. Alternatively, thethickness of the electron transport layer (electron supply layer) may belarger than that of the hole transport layer (hole supply layer). As aresult, an electron can be supplied sufficiently to the light emittinglayer in an amount necessary for a high efficiency at a low drivingvoltage. That is, by disposing a hole transport layer between the firstelectrode corresponding to an anode electrode and the light emittinglayer, and forming the hole transport layer with a film having a filmthickness smaller than the electron transport layer, supply of holes canbe increased. Then, this makes it possible to obtain a carrier balancewith no excess or deficiency of holes and electrons and a sufficientlylarge carrier supply amount. Therefore, a high emission efficiency canbe obtained. In addition, due to no excess or deficiency of holes andelectrons, the carrier balance hardly collapses, drive deterioration issuppressed, and an emission lifetime can be prolonged.

The first electrode is disposed on the interlayer insulation layer, asdescribed above. In addition, the interlayer insulation layer covers alight emitting element driving unit formed on the first substrate. Thelight emitting element driving unit is constituted by one or moretransistors (for example, MOSFET or TFT). The transistors areelectrically connected to the first electrode via a contact hole(contact plug) disposed in the interlayer insulation layer, as describedabove. The light emitting element driving unit can have a known circuitconfiguration. As a constituent material of the interlayer insulationlayer, an SiO₂-based material such as SiO₂, BPSG, PSG, BSG, AsSG, PbSG,SOG (spin on glass), low melting point glass, or glass paste; anSiN-based material including an SiON-based material; or an insulatingresin such as an acrylic resin or a polyimide resin can be used singlyor in combination thereof appropriately. For forming the interlayerinsulation layer, a known process such as a CVD method, a coatingmethod, a sputtering method, or various printing methods can be used.

An insulating or conductive protective film is preferably disposed abovethe second electrode in order to prevent moisture from reaching theorganic layer. The protective film is preferably formed particularly onthe basis of a film formation method in which the energy of filmformation particles is small, such as a vacuum vapor deposition method,or a film formation method such as a CVD method or an MOCVD methodbecause an influence on a base can be reduced. Alternatively, in orderto prevent degradation of brightness due to deterioration of the organiclayer, a film formation temperature is desirably set to roomtemperature. Furthermore, in order to prevent peeling of the protectivefilm, the protective film is desirably formed under a conditionminimizing a stress of the protective film. In addition, the protectivefilm is preferably formed without exposure of an already formedelectrode to the atmosphere. As a result, degradation of the organiclayer due to moisture or oxygen in the atmosphere can be prevented.Furthermore, the protective film is desirably constituted by a materialthat transmits light generated in the organic layer by, for example, 80%or more. Specific examples of the material include an inorganicamorphous insulating material such as the following materials. Such aninorganic amorphous insulating material does not generate grains, andtherefore has low water permeability and constitutes a good protectivefilm. Specifically, as a material constituting the protective film, amaterial that is transparent to light emitted from the light emittinglayer, is dense, and does not transmit moisture is preferably used. Morespecific examples of the material include amorphous silicon (α-Si),amorphous silicon carbide (α-SiC), amorphous silicon nitride(α-Si_(1-x)N_(x)), amorphous silicon oxide (α-Si_(1-y)O_(y)), amorphouscarbon (α-C), amorphous silicon oxide/nitride (α-SiON), and Al₂O₃. In acase where the protective film is constituted by a conductive material,the protective film is only required to be constituted by a transparentconductive material such as ITO or IZO. The protective film and thesecond substrate are bonded to each other, for example, via a resinlayer (sealing resin layer). Examples of a material constituting theresin layer (sealing resin layer) include a thermosetting adhesive suchas an acrylic adhesive, an epoxy adhesive, a urethane adhesive, asilicone adhesive, or a cyanoacrylate adhesive, and an ultravioletcurable adhesive.

On an outermost surface of the display device, an ultraviolet absorbinglayer, a contamination preventing layer, a hard coat layer, and anantistatic layer may be formed, or a protective member may be disposed.

The display device may have a resonator structure in order to furtherimprove a light extraction efficiency. Specifically, light emitted fromthe light emitting layer is caused to resonate between a first interfaceconstituted by an interface between the first electrode and the organiclayer (or an interface between a light reflecting layer disposed belowthe first electrode via an interlayer insulation layer and theinterlayer insulation layer) and a second interface constituted by aninterface between the second electrode and the organic layer, and a partof the light is emitted from the second electrode. Then, when a distancefrom a maximum emission position of the light emitting layer to thefirst interface is represented by L₁, an optical distance thereof isrepresented by OL₁, a distance from the maximum emission position of thelight emitting layer to the second interface is represented by L₂, anoptical distance thereof is represented by OL₂, and m₁ and m₂ eachrepresent an integer, the following formulas (1-1), (1-2), (1-3), and(1-4) are satisfied.

0.7{−Φ₁/(2π)+m ₁}≤2×OL ₁/λ≤1.2{−Φ₁/(2π)+m ₁}  (1-1)

0.7{−Φ₂/(2π)+m ₂}≤2×OL ₂/λ≤1.2{−Φ₂/(2π)+m ₂}  (1-2)

L ₁ <L ₂  (1-3)

m ₁ <m ₂  (1-4)

Herein,

λ: Maximum peak wavelength of a spectrum of light generated in the lightemitting layer (or a desired wavelength among wavelengths of lightgenerated in the light emitting layer)

Φ₁: Phase shift amount (unit: radian) of light reflected on the firstinterface

Provided that −2π<Φ₁≤0.

Φ₂: Phase shift amount (unit: radian) of light reflected on the secondinterface

Provided that −2π<Φ₂≤0.

Incidentally, the distance L₁ from the maximum emission position of thelight emitting layer to the first interface means an actual distance(physical distance) from the maximum emission position of the lightemitting layer to the first interface and the distance L₂ from themaximum emission position of the light emitting layer to the secondinterface means an actual distance (physical distance) from the maximumemission position of the light emitting layer to the second interface.In addition, the optical distance is also called an optical path length,and generally refers to n×L when a light ray passes through a mediumhaving a refractive index n for a distance L. The same applies to thefollowing description. Therefore, when an average refractive index isrepresented by n₀, the following relations are satisfied.

OL ₁ =L ₁ ×n ₀

OL ₂ =L ₂ ×n ₀

Herein, the average refractive index n₀ is obtained by summing up aproduct of the refractive index and the thickness of each layerconstituting the organic layer and various interlayer insulation layers,and dividing the resulting sum by the thickness of the organic layer andthe various interlayer insulation layers. In addition, the secondelectrode may be formed of a semi-light transmitting material and mayhave a form of m₁=0 and m₂=1 in which a light extraction efficiency canbe maximized.

The light reflecting layer and the second electrode absorb a part ofincident light and reflect the rest. Therefore, a phase shift occurs inthe reflected light. The phase shift amounts Φ₁ and Φ₂ can be determinedby measuring values of a real number part and an imaginary number partof a complex refractive index of each of materials constituting thelight reflecting layer and the second electrode, for example, using anellipsometer, and performing calculation based on these values (See, forexample, “Principles of Optic”, Max Born and Emil Wolf, 1974 (PERGAMONPRESS)). Note that the refractive index of the organic layer, variousinterlayer insulation layers, or the like can also be determined bymeasurement with an ellipsometer.

As described above, in an organic EL display device having a resonatorstructure, actually, a red light emitting element constituted byinclusion of a red color filter in a white light emitting element causesred light emitted from the light emitting layer to resonate, and emitsreddish light (light having a light spectrum peak in a red region) fromthe second electrode. In addition, the green light emitting elementconstituted by inclusion of a green color filter in a white lightemitting element causes green light emitted from the light emittinglayer to resonate, and emits greenish light (light having a lightspectrum peak in a green region) from the second electrode. In addition,the blue light emitting element constituted by inclusion of a blue colorfilter in a white light emitting element causes blue light emitted fromthe light emitting layer to resonate, and emits blueish light (lighthaving a light spectrum peak in a blue region) from the secondelectrode. That is, it is only required to design each light emittingelement by determining a desired wavelength A (specifically, wavelengthsof red light, green light, and blue light) among wavelengths of lightgenerated in the light emitting layer and determining various parameterssuch as OL₁ and OL₂ in each of the red light emitting element, the greenlight emitting element, and the blue light emitting element on the basisof formulas (1-2), (1-2), (1-3), and (1-4).

Examples of a material constituting the light reflecting layer includealuminum, an aluminum alloy (for example, Al—Nd), a Ti/Al laminationstructure, chromium (Cr), silver (Ag), and a silver alloy (for example,Ag—Pd—Cu or Ag—Sm—Cu). The light reflecting layer can be formed, forexample, by a vapor deposition method including an electron beam vapordeposition method, a hot filament vapor deposition method, and a vacuumvapor deposition method, a sputtering method, a CVD method, and an ionplating method; a plating method (an electroplating method or anelectroless plating method); a lift-off method; a laser ablation method;a sol-gel method, or the like.

The display device can be used, for example, as a monitor deviceconstituting a personal computer, or a monitor device incorporated in atelevision receiver, a mobile phone, a personal digital assistant (PDA),or a game machine. Alternatively, the display device can be applied toan electronic view finder (EVF) or a head mounted display (HMD).

First Embodiment

A first embodiment relates to a light emitting element (specifically,organic EL element) of the present disclosure and a display device(specifically, an organic EL display device) of the present disclosure.FIG. 1 illustrates a schematic partial cross-sectional view of a displaydevice of the first embodiment (hereinafter, also referred to as anorganic EL display device). FIG. 2 illustrates an enlarged schematicpartial cross-sectional view of a first insulation layer, a secondinsulation layer, a third insulation layer, and the like in a lightemitting element constituting the display device of the firstembodiment. FIG. 3 illustrates an enlarged schematic partialcross-sectional view of an organic layer and the like. The organic ELdisplay device of the first embodiment is an active matrix type colordisplay organic EL display device, and is a top emission type displaydevice. That is, light is emitted through an second electrode.

In the organic EL display device of the first embodiment, a plurality oflight emitting elements 11 of the first embodiment described below isarranged in a two-dimensional matrix. Alternatively, in anotherexpression, the organic EL display device of the first embodimentincludes a first substrate 21, a second substrate 23, and an imagedisplay unit 10 sandwiched by the first substrate 21 and the secondsubstrate 23. In the image display unit 10, the plurality of lightemitting elements 11 of the first embodiment described below is arrangedin a two-dimensional matrix. The light emitting elements 11 are formedon a side of the first substrate.

Each of the light emitting elements 11 of the first embodiment includes:

a first electrode 22 formed on a base body;

a first insulation layer 41 formed on the base body and the firstelectrode 22 and having an aperture portion 41A in which a part of thefirst electrode 22 is exposed;

a second insulation layer 42 formed on the first insulation layer 41 andhaving a protruding end portion 42A protruding from the aperture portion41A disposed in the first insulation layer 41;

a third insulation layer 43 formed on the second insulation layer 42 andhaving an end portion 43A recessed from the protruding end portion 42Aof the second insulation layer 42;

a charge injection/transport layer 51 formed over the second insulationlayer 42 and the third insulation layer 43 from the first electrode 22;

an organic layer 52 formed on the charge injection/transport layer 51and including a light emitting layer formed of an organic light emittingmaterial; and

a second electrode 24 formed on the organic layer 52, and

at least a part of the charge injection/transport layer 51 isdiscontinuous at the protruding end portion 42A of the second insulationlayer 42.

In the first embodiment, a material constituting the first insulationlayer 41, a material constituting the second insulation layer 42, and amaterial constituting the third insulation layer 43 are different fromone another. Specifically, the insulation layers 41, 42, and 43 areconstituted by a material in which the second insulation layer 42 andthe third insulation layer 43 are hardly etched when the firstinsulation layer 41 is etched, a material in which the first insulationlayer 41 and the third insulation layer 43 are hardly etched when thesecond insulation layer 42 is etched, and a material in which the firstinsulation layer 41 and the second insulation layer 42 are hardly etchedwhen the third insulation layer 43 is etched. A specific combination of(material constituting the first insulation layer 41, materialconstituting the second insulation layer 42, and material constitutingthe third insulation layer 43) is (SiN-based material, SiC-basedmaterial, and SiO₂-based material). In addition, a thickness T₂ of thesecond insulation layer 42 above the first electrode 22 is smaller thaneach of thicknesses T₁ and T₃ of the first insulation layer 41 and thethird insulation layer 43 above the first electrode 22. Specifically,the first insulation layer 41 having the thickness T₁ of 30 nm above thefirst electrode 22 is formed of SiN, the second insulation layer 42having the thickness T₂ of 20 nm above the first electrode 22 is formedof SiC, and the third insulation layer 43 having the thickness T₃ of 50nm above the first electrode 22 is formed of SiO₂. A length L₂ of theprotruding end portion 42A of the second insulation layer 42 protrudingfrom the aperture portion 41A is, for example, 100 nm. In addition, arelation (aspect ratio) between the length L₂ of the protruding endportion 42A of the second insulation layer 42 and the thickness T₁ ofthe first insulation layer 41 is L₂/T₁=3.3. An aperture portion edgeportion projection image is included in a third insulation layer edgeportion projection image. In other words, the end portion 43A of thethird insulation layer 43 protrudes more than an edge portion 41B of theaperture portion 41A. A distance (protrusion amount) from the apertureportion edge portion projection image to the third insulation layer edgeportion projection image is, for example, 50 nm. The planar shape of theaperture portion 41A is, for example, a rectangular shape in which thefour corners of 2 μm×2 μm are rounded, or a circular shape with adiameter of 2 μm. The charge injection/transport layer 51 or a part ofthe organic layer 52 may be formed in a region surrounded by theprotruding end portion 42A of the second insulation layer 42, the edgeportion 41B of the aperture portion 41 disposed in the first insulationlayer 41, and the first electrode 22. However, in the exampleillustrated in FIG. 1, the region is a vacant space.

In addition, top surfaces of the second insulation layer 42 and thethird insulation layer 43 in the region beyond the third insulationlayer 43 from the protruding end portion 42A of the second insulationlayer 42 are gentle.

FIGS. 12A and 12B illustrate simulation results of an electric fieldconcentration state in a case where a top surface of the part of anorganic layer positioned above a region beyond the third insulationlayer from the protruding end portion of the second insulation layer isnot gentle and in a case where the top surface is gentle, respectively.The sizes in FIGS. 12A and 12B correspond to 250 nm in length and 250 nmin width. In FIG. 12A, when the electric field intensity at an endportion of the aperture portion as a region surrounded by “A” was “1”,the electric field intensity of a region of the organic layer surroundedby “B” with a not gentle top surface was 0.92. Meanwhile, in FIG. 12B,the electric field intensity at an end portion of the aperture portionas a region surrounded by “C” was 0.78, and the electric field intensityin a region surrounded by “D” as a region above the third insulationlayer was 0.81. The electric field intensities of organic layer regionssurrounded by “E” and “F” with gentle top surfaces were 0.64 and 0.66,respectively. Note that the edge portion of the aperture portiondisposed in the first insulation layer is omitted in the simulation ofthe example illustrated in FIG. 12B. As described above, it is foundthat, by making the top surfaces of the second insulation layer 42 andthe third insulation layer 43 in the region beyond the third insulationlayer 43 from the protruding end portion 42A of the second insulationlayer 42 gentle, the organic layer 52 and the second electrode 24 formedthereon become gentle and concentration of an electric field formed bythe first electrode 22 and the second electrode 24 in the light emittinglayer can be suppressed.

Herein, the resistance of the charge injection/transport layer 51 isincreased due to discontinuity in at least a part of the chargeinjection/transport layer 51 at the protruding end portion 42A of thesecond insulation layer 42. The entire charge injection/transport layer51 may be discontinuous at the protruding end portion 42A of the secondinsulation layer 42.

In the first embodiment, the organic layer 52 has a lamination structureof a hole transport layer (HTL), a light emitting layer, an electrontransport layer (ETL), and an electron injection layer (EIL) from a sideof the charge injection/transport layer. The light emitting layer isconstituted by at least two light emitting layers that emit differentcolors, and light emitted from the organic layer 52 is white.Specifically, the light emitting layer has a structure in which threelayers of a red light emitting layer that emits red light, a green lightemitting layer that emits green light, and a blue light emitting layerthat emits blue light are laminated. The light emitting layer may have astructure in which two layers of a blue light emitting layer that emitsblue light and a yellow light emitting layer that emits yellow light arelaminated or a structure in which two layers of a blue light emittinglayer that emits blue light and an orange light emitting layer thatemits orange light are laminated. A light emitting element to display ared color (red light emitting element 11R) includes a red color filter12R. A light emitting element to display a green color (green lightemitting element 11G) includes a green color filter 12G. A lightemitting element to display a blue color (blue light emitting element11B) includes a blued color filter 12B. The red light emitting element11R, the green light emitting element 11G, and the blue light emittingelement 11B have the same configuration and structure except for thecolor filters. A black matrix layer (light shielding layer) 13 is formedbetween a color filter 12 and a color filter 12. In addition, the colorfilter 12 and the black matrix layer 13 are formed on a surface side ofthe second substrate 23 opposed to the first substrate 21. This makes itpossible to shorten a distance between the light emitting layer and thecolor filter 12 and to suppress color mixing caused by incidence oflight emitted from the light emitting layer on an adjacent color filter12 of another color.

In the first embodiment, the charge injection/transport layer 51exhibits at least one of a charge injection property and a chargetransport property. Specifically, the charge injection/transport layer51 is constituted by a hole injection layer (HIL).

The charge injection/transport layer 51 functioning as a hole injectionlayer is a layer that increases a hole injection efficiency, functionsas a buffer layer for preventing leakage, and has a thickness of about 2nm to 10 nm, for example. The hole injection layer is formed of ahexaazatriphenylene derivative represented by the following formula (A)or (B), for example.

Herein, R¹ to R⁶ each independently represent a substituent selectedfrom a hydrogen atom, a halogen atom, a hydroxy group, an amino group,an arulamino group, a substituted or unsubstituted carbonyl group having20 or less carbon atoms, a substituted or unsubstituted carbonyl estergroup having 20 or less carbon atoms, a substituted or unsubstitutedalkyl group having 20 or less carbon atoms, a substituted orunsubstituted alkenyl group having 20 or less carbon atoms, asubstituted or unsubstituted alkoxy group having 20 or less carbonatoms, a substituted or unsubstituted aryl group having 30 or lesscarbon atoms, a substituted or unsubstituted heterocyclic group having30 or less carbon atoms, a nitrile group, a cyano group, a nitro group,and a silyl group, and adjacent R^(m)s (m=1 to 6) may be bonded to eachother via a cyclic structure. In addition, X¹ to X⁶ each independentlyrepresent a carbon atom or a nitrogen atom.

The hole transport layer is a layer that increases a hole transportefficiency to the light emitting layer. When an electric field isapplied to the light emitting layer, recombination of electrons andholes occurs to generate light. The electron transport layer is a layerthat increases an electron transport efficiency to the light emittinglayer, and the electron injection layer is a layer that increases anelectron injection efficiency to the light emitting layer.

The hole transport layer is formed of4,4′,4″-tris(3-methylphenylphenylamino) triphenylamine <m-MTDATA> orα-naphthylphenyl diamine <αNPD> having a thickness of about 40 nm, forexample.

The light emitting layer is a light emitting layer that generates whitelight by color mixing, and is formed by laminating a red light emittinglayer, a green light emitting layer, and a blue light emitting layer asdescribed above, for example.

When an electric field is applied to the red light emitting layer, apart of holes injected from the first electrode 22 and a part ofelectrons injected from the second electrode 24 are recombined togenerate red light. Such a red light emitting layer contains at leastone kind of material among a red light emitting material, a holetransport material, an electron transport material, and a both chargetransport material, for example. The red light emitting material may bea fluorescent material or a phosphorescent material. The red lightemitting layer having a thickness of about 5 nm is formed by mixing 30%by mass of 2,6-bis[(4′-methoxydiphenylamino)styryl]-1,5-dicyanonaphthalene <BSN> with 4,4-bis(2,2-diphenylvinin)biphenyl <DPVBi>, for example.

When an electric field is applied to the green light emitting layer, apart of holes injected from the first electrode 22 and a part ofelectrons injected from the second electrode 24 are recombined togenerate green light. Such a green light emitting layer contains atleast one kind of material among a green light emitting material, a holetransport material, an electron transport material, and a both chargetransport material, for example. The green light emitting material maybe a fluorescent material or a phosphorescent material. The green lightemitting layer having a thickness of about 10 nm is formed by mixing 5%by mass of coumarin 6 with DPVBi, for example.

When an electric field is applied to the blue light emitting layer, apart of holes injected from the first electrode 22 and a part ofelectrons injected from the second electrode 24 are recombined togenerate blue light. Such a blue light emitting layer contains at leastone kind of material among a blue light emitting material, a holetransport material, an electron transport material, and a both chargetransport material, for example. The blue light emitting material may bea fluorescent material or a phosphorescent material. The blue lightemitting layer having a thickness of about 30 nm is formed by mixing2.5% by mass of 4,4′-bis [2-{4-(N,N-diphenylamino) phenyl} vinyl]biphenyl <DPAVBi> with DPVBi.

The electron transport layer having a thickness of about 20 nm is formedof 8-hydroxyquinoline aluminum <Alq 3>, for example. The electroninjection layer having a thickness of about 0.3 nm is formed of LiF orLi₂O, for example.

Each of the light emitting elements 11 may have a resonator structure inwhich the organic layer 52 is a resonance part. In this case, in orderto appropriately adjust a distance from a light emitting surface to areflecting surface (specifically, the first electrode 22 and the secondelectrode 24), the thickness of the organic layer 52 is preferably8×10⁻⁸ m or more and 5×10⁻⁷ m or less, and more preferably 1.5×10⁻⁷ m ormore and 3.5×10⁻⁷ m or less.

In addition, the first insulation layer 41, the second insulation layer42, the third insulation layer 43, the charge injection/transport layer51, the organic layer 52, and the second electrode 24 are common in theplurality of light emitting elements. That is, these layers 41, 42, 43,51, and 52 and the second electrode 24 are not patterned and are in aso-called solid film state. As described above, by forming a solid filmof a light emitting layer common in all the light emitting elementswithout forming the light emitting layer separately for each lightemitting element (patterning formation), the light emitting elements canalso correspond to a small and high-resolution display device having afield angle of several inches or less and a pixel pitch of several tensof micrometers or less, for example.

An insulating or conductive protection film 26 (specifically, formed ofan SiO₂-based material or an SiN-based material, for example) isdisposed above the second electrode 24 in order to prevent moisture fromreaching the organic layer 52. Furthermore, the protective film 26 andthe second substrate 23 are bonded to each other via a resin layer(sealing resin layer) 27 formed of an epoxy adhesive, for example. Thefirst electrode 22 functioning as an anode electrode is formed ofaluminum (Al—Ni alloy) having a thickness of 0.1 μm. The secondelectrode 24 functioning as a cathode electrode is formed of an Mg—Agalloy having a thickness of 10 nm.

In the first embodiment, the base body is constituted by a siliconsemiconductor substrate (first substrate 21) on which a transistor(specifically, MOSFET, for example) 30 is formed and an interlayerinsulation layer 25 formed of SiO₂ formed thereon. The first electrode22 and the first insulation layer 41 are formed on the interlayerinsulation layer 25. The first electrode 22 and the transistor 30 formedon the silicon semiconductor substrate (first substrate 21) areconnected to each other via a contact hole 36 formed in the interlayerinsulation layer 25. Herein, the transistor 30 formed of a MOSFET isconstituted by a gate electrode 31, a gate insulation layer 32, achannel formation region 33, and a source/drain region 34. An elementisolation region 35 is formed between the transistors 30, and thetransistors 30 are thereby separated from each other.

Hereinafter, the outline of a method for manufacturing the organic ELdisplay device of the first embodiment will be described.

[Step-100]

First, a light emitting element driving unit is formed on a siliconsemiconductor substrate (first substrate 21) on the basis of a knownMOSFET manufacturing process, and then the interlayer insulation layer25 is formed on the entire surface on the basis of a CVD method. Then,in the portion of the interlayer insulation layer 25 positioned aboveone of source/drain regions of the transistor 30, a connection hole isformed on the basis of a photolithography technique and an etchingtechnique. Thereafter, a metal layer is formed on the interlayerinsulation layer 25 including the connection hole on the basis of asputtering method, for example. Subsequently, the metal layer ispatterned on the basis of a photolithography technique and an etchingtechnique, and the first electrode 22 can be thereby formed on theinterlayer insulation layer 25 (see FIG. 4). The first electrode 22 isseparated for each light emitting element.

[Step-110]

Thereafter, a first insulation layer forming layer 44, a secondinsulation layer forming layer 45, and a third insulation layer forminglayer 46 are sequentially formed on the entire surface according to aCVD method (see FIG. 5). Subsequently, the third insulation layerforming layer 46 is patterned on the basis of a photolithographytechnique and an etching technique. Specifically, a resist layer isformed on the third insulation layer forming layer 46, and the resistlayer is patterned on the basis of a photolithography technique. Then,the third insulation layer forming layer 46 is anisotropically etchedusing the patterned resist layer as an etching mask, and then the resistlayer is removed. In this way, the structure illustrated in FIG. 6 canbe obtained.

Thereafter, the second insulation layer forming layer 45 is patterned onthe basis of a photolithography technique and an etching technique.Specifically, a resist layer is formed on the second insulation layerforming layer 45, and the resist layer is patterned by aphotolithography technique. Then, the second insulation layer forminglayer 45 is anisotropically etched using the patterned resist layer asan etching mask, and then the resist layer is removed. In this way, thestructure illustrated in FIG. 7 can be obtained.

Furthermore, the first insulation layer forming layer 44 is patterned onthe basis of a photolithography technique and an etching technique.Specifically, a resist layer is formed on the first insulation layerforming layer 44, and the resist layer is patterned by aphotolithography technique. Then, the first insulation layer forminglayer 44 is isotropically etched using the patterned resist layer as anetching mask, and then the resist layer is removed. In this way, thestructure illustrated in FIG. 2 can be obtained.

[Step-120]

Subsequently, the charge injection/transport layer 51 is formed on theentire surface on the basis of a PVD method such as a vacuum vapordeposition method. At this time, the charge injection/transport layer 51is cut at the protruding end portion 42A of the second insulation layer42, or is partially connected with an extremely thin film. As describedabove, the protruding end portion 42A of the second insulation layer 42can form the charge injection/transport layer 51 in a reliably separatedstate for each of the first electrodes 22 (for each of the lightemitting elements 11) without separately performing patterning.

[Step-130]

Thereafter, a film of the organic layer 52 is formed on the chargeinjection/transport layer 51 by a PVD method such as a vacuum vapordeposition method or a sputtering method, or a coating method such as aspin coating method or a die coating method, for example. At this time,apart (for example, a hole transport layer) of the organic layer 52 maybe cut by the protruding end portion 42A. However, FIG. 1 illustrates astate in which the entire organic layer 52 is connected without beingcut.

[Step-140]

Subsequently, the second electrode 24 is formed on the entire surface ofthe organic layer 52 on the basis of a vacuum vapor deposition method,for example. In this way, films of the organic layer 52 and the secondelectrode 24 can be continuously formed on the first electrode 22, forexample, in a vacuum atmosphere. Thereafter, the protective film 26 isformed on the entire surface by a CVD method or a PVD method, forexample. Finally, the protective film 26 and the second electrode 22 arebonded to each other via the resin layer (sealing resin layer) 27. Notethat the color filters 12R, 12G, and 12B and the black matrix layer 13are formed in advance on the second substrate 23. Then, a surface onwhich the color filter 12 is formed is used as a bonding surface. Inthis way, the organic EL display device illustrated in FIG. 1 can beobtained.

As described above, in the first embodiment, the protruding end portion42A protruding from the aperture portion 41A (that is, the protrudingend portion 42A protruding from the first insulation layer 41 and thethird insulation layer 43) is disposed in the second insulation layer 42sandwiched by the first insulation layer 41 and the third insulationlayer 43. Therefore, at least a part of the charge injection/transportlayer 51 formed over the second insulation layer 42 and the thirdinsulation layer 43 from the first electrode 22 is reliablydiscontinuous at the protruding end portion 42A. That is, the chargeinjection/transport layer 51 is reliably cut at the protruding endportion 42A of the second insulation layer 42 or the resistance thereofis increased, and therefore occurrence of a phenomenon that a leakagecurrent flows between the first electrode 22 of a certain light emittingelement and the second electrode 24 constituting an adjacent lightemitting element can be reliably prevented. In addition, thechromaticity of the entire pixels does not deviate from a desiredchromaticity, and the chromaticity of white light emitted from the whitelight emitting element can be improved.

Second Embodiment

The second embodiment is a modification of the first embodiment. In alight emitting element of the second embodiment, a material constitutingthe first insulation layer 41 is different from a material constitutingthe second insulation layer 42 and a material constituting the thirdinsulation layer 43, and the material constituting the second insulationlayer 42 and the material constituting the third insulation layer 43 arethe same as each other. Specifically, the insulation layers 41, 42, and43 are constituted by a material in which the second insulation layer 42and the third insulation layer 43 are hardly etched when the firstinsulation layer 41 is etched, and a material in which the firstinsulation layer 41 is hardly etched when the second insulation layer 42and the third insulation layer 43 are etched. More specifically, thematerial constituting the first insulation layer 41 is formed of SiN,and the material constituting the second insulation layer 42 and thethird insulation layer 43 is formed of SiO₂. The configurations andstructures of the display device and the light emitting element of thesecond embodiment can be similar to those of the display device and thelight emitting element of the first embodiment except for the abovepoints, and therefore detailed description will be omitted.

Hereinafter, the outline of a method for manufacturing the organic ELdisplay device of the second embodiment will be described.

[Step-200]

First, in a similar manner to [Step-100] of the first embodiment, alight emitting element driving unit is formed on a silicon semiconductorsubstrate (first substrate 21) on the basis of a known MOSFETmanufacturing process, and then an interlayer insulation layer 25 and afirst electrode 22 are formed.

[Step-210]

Thereafter, a first insulation layer forming layer 47 and a second/thirdinsulation layer forming layer 48 are sequentially formed on the entiresurface according to a CVD method. Subsequently, a resist layer 49 isformed on the second/third insulation layer forming layer 48, and theresist layer is patterned by a photolithography technique to form aforward tapered resist layer 49 having an aperture portion 49A (see FIG.8). Then, the second/third insulation layer forming layer 48 isanisotropically etched using the patterned resist layer 49 as an etchingmask, and then the resist layer is removed. In this way, the structureillustrated in FIG. 9 can be obtained.

Thereafter, the first insulation layer forming layer 47 is patterned onthe basis of a photolithography technique and an etching technique.Specifically, a resist layer is formed on the first insulation layerforming layer 47, and the resist layer is patterned by aphotolithography technique. Then, the first insulation layer forminglayer 47 is isotropically etched using the patterned resist layer as anetching mask, and then the resist layer is removed. In this way, thestructure illustrated in FIG. 10 can be obtained.

[Step-220]

Subsequently, by performing similar steps to [Step-120], [Step-130], and[Step-140] of the first embodiment, the organic EL display device of thesecond embodiment can be obtained.

As described above, even in the second embodiment, the protruding endportion 42A protruding from the aperture portion 41A (that is, theprotruding end portion 42A protruding from the first insulation layer 41and the third insulation layer 43) is disposed in the second insulationlayer 42 sandwiched by the first insulation layer 41 and the thirdinsulation layer 43. Therefore, at least a part of the chargeinjection/transport layer 51 formed over the second insulation layer 42and the third insulation layer 43 from the first electrode 22 isreliably discontinuous at the protruding end portion 42A. That is, thecharge injection/transport layer 51 is reliably cut at the protrudingend portion 42A of the second insulation layer 42 or the resistancethereof is increased, and therefore occurrence of a phenomenon that aleakage current flows between the first electrode 22 of a certain lightemitting element and the second electrode 24 constituting an adjacentlight emitting element can be reliably prevented. In addition, thechromaticity of the entire pixels does not deviate from a desiredchromaticity, and the chromaticity of white light emitted from the whitelight emitting element can be improved.

FIG. 11 illustrates a cross-sectional photograph of the first electrodeor the like constituting the light emitting element at the time when[Step-210] is completed. The tip portion of the protruding end portion42A of the second insulation layer 42 is bent slightly downward when asample for photographing is prepared. However, it is clearly found thatthe protruding end portion 42A protruding from the aperture portion 41Ais disposed in the second insulation layer 42 sandwiched by the firstinsulation layer 41 and the third insulation layer 43.

Hitherto, the present disclosure has been described on the basis of thepreferable embodiments. However, the present disclosure is not limitedto these embodiments. The configurations and structures of the displaydevice, the organic EL display device, the light emitting element, andthe organic EL element described in the embodiments are illustrative andcan be changed appropriately. The first insulation layer may beconstituted by two layers of a lower first insulation layer and an upperfirst insulation layer, the lower first insulation layer that is thepart of the interlayer insulation layer 25 exposed between the firstelectrode 22 and the first electrode 22 may be formed, and the flatupper first insulation layer may be formed on the lower first insulationlayer and an edge portion of the first electrode. In the embodiment, asub-pixel is constituted exclusively by combining a white light emittingelement with a color filter. Alternatively, one pixel may be constitutedby three sub-pixels (light emitting elements) of a sub-pixel having ared light emitting layer and constituted by a light emitting elementthat emits red light, a sub-pixel having a green light emitting layerand constituted by a light emitting element that emits green light, anda sub-pixel having a blue light emitting layer and constituted by alight emitting element that emits blue light.

Note that the present disclosure may have the following configurations.

[A01]<<Light Emitting Element>>

A light emitting element including:

a first electrode formed on a base body;

a first insulation layer formed on the base body and the first electrodeand having an aperture portion in which a part of the first electrode isexposed;

a second insulation layer formed on the first insulation layer andhaving a protruding end portion protruding from the aperture portiondisposed in the first insulation layer;

a third insulation layer formed on the second insulation layer andhaving an end portion recessed from the protruding end portion of thesecond insulation layer;

a charge injection/transport layer formed over the second insulationlayer and the third insulation layer from the first electrode;

an organic layer formed on the charge injection/transport layer andincluding a light emitting layer formed of an organic light emittingmaterial; and

a second electrode formed on the organic layer, in which

at least apart of the charge injection/transport layer is discontinuousat the protruding end portion of the second insulation layer.

[A02] The light emitting element according to [A01], in which topsurfaces of the second insulation layer and the third insulation layerin a region beyond the third insulation layer from the protruding endportion of the second insulation layer are gentle.

[A03] The light emitting element according to [A01] or [A02], in which amaterial constituting the first insulation layer, a materialconstituting the second insulation layer, and a material constitutingthe third insulation layer are different from one another.

[A04] The light emitting element according to [A01] or [A02], in which amaterial constituting the first insulation layer is different from amaterial constituting the second insulation layer and a materialconstituting the third insulation layer, and the material constitutingthe second insulation layer and the material constituting the thirdinsulation layer are the same as each other.

[A05] The light emitting element according to any one of [A01] to [A04],in which the resistance of the charge injection/transport layer isincreased due to discontinuity in at least a part of the chargeinjection/transport layer at the protruding end portion of the secondinsulation layer.

[A06] The light emitting element according to any one of [A01] to [A05],in which the thickness of the second insulation layer above the firstelectrode is smaller than the thicknesses of the first insulation layerand the third insulation layer above the first electrode.

[A07] The light emitting element according to any one of [A01] to [A06],in which the light emitting layer is constituted by at least two lightemitting layers that emit different colors.

[A08] The light emitting element according to [A07], in which lightemitted from the organic layer is white.

[A09] The light emitting element according to any one of [A01] to [A08],in which the charge injection/transport layer exhibits at least one of acharge injection property and a charge transport property.

[A10] The light emitting element according to any one of [A01] to [A09],in which

the base body is formed of a silicon semiconductor substrate on which atransistor is formed and an interlayer insulation layer formed thereon,

the first electrode and the first insulation layer are formed on theinterlayer insulation layer, and

the first electrode is connected to the transistor formed on the siliconsemiconductor substrate via a contact hole formed in the interlayerinsulation layer.

[B01]<<Display Device>>

A display device in which a plurality of the light emitting elementsaccording to any one of [A01] to [A10] is arranged in a two-dimensionalmatrix.

[B02] The display device according to [B01], in which the firstinsulation layer, the second insulation layer, the third insulationlayer, the charge injection/transport layer, the organic layer, and thesecond electrode are common in the plurality of light emitting elements.

REFERENCE SIGNS LIST

-   10 Image display unit-   11 Light emitting element-   11R Red light emitting element-   11G Green light emitting element-   11B Blue light emitting element-   12R Red color filter-   12G Green color filter-   12B Blue color filter-   13 Black matrix layer-   21 First substrate-   22 First electrode-   23 Second substrate-   24 Second electrode-   25 Interlayer insulation layer-   26 Protective film-   27 Resin layer (sealing resin layer)-   30 Transistor (MOSFET)-   31 Gate electrode-   32 Gate insulation layer-   33 Channel formation region-   34 Source/drain region-   35 Element isolation region-   36 Contact hole-   41 First insulation layer-   42 Aperture portion disposed in first insulation layer-   42A Edge portion of aperture portion-   43 Second insulation layer-   42A Protruding end portion-   43 Third insulation layer-   43A End portion of third insulation layer-   44, 47 First insulation layer forming layer-   45 Second insulation layer forming layer-   46 Third insulation layer forming layer-   48 Second/third insulation layer forming layer-   49 Resist layer-   49A Aperture portion disposed in resist layer-   51 Charge injection/transport layer-   52 Organic layer

1. A light emitting element comprising: a first electrode formed on abase body; a first insulation layer formed on the base body and thefirst electrode and having an aperture portion in which a part of thefirst electrode is exposed; a second insulation layer formed on thefirst insulation layer and having a protruding end portion protrudingfrom the aperture portion disposed in the first insulation layer; athird insulation layer formed on the second insulation layer and havingan end portion recessed from the protruding end portion of the secondinsulation layer; a charge injection/transport layer formed over thesecond insulation layer and the third insulation layer from the firstelectrode; an organic layer formed on the charge injection/transportlayer and including a light emitting layer formed of an organic lightemitting material; and a second electrode formed on the organic layer,wherein at least a part of the charge injection/transport layer isdiscontinuous at the protruding end portion of the second insulationlayer.
 2. The light emitting element according to claim 1, wherein topsurfaces of the second insulation layer and the third insulation layerin a region beyond the third insulation layer from the protruding endportion of the second insulation layer are gentle.
 3. The light emittingelement according to claim 1, wherein a material constituting the firstinsulation layer, a material constituting the second insulation layer,and a material constituting the third insulation layer are differentfrom one another.
 4. The light emitting element according to claim 1,wherein a material constituting the first insulation layer is differentfrom a material constituting the second insulation layer and a materialconstituting the third insulation layer, and the material constitutingthe second insulation layer and the material constituting the thirdinsulation layer are the same as each other.
 5. The light emittingelement according to claim 1, wherein the resistance of the chargeinjection/transport layer is increased due to discontinuity in at leasta part of the charge injection/transport layer at the protruding endportion of the second insulation layer.
 6. The light emitting elementaccording to claim 1, wherein the thickness of the second insulationlayer above the first electrode is smaller than each of the thicknessesof the first insulation layer and the third insulation layer above thefirst electrode.
 7. The light emitting element according to claim 1,wherein the light emitting layer is constituted by at least two lightemitting layers that emit different colors.
 8. The light emittingelement according to claim 7, wherein light emitted from the organiclayer is white.
 9. The light emitting element according to claim 1,wherein the charge injection/transport layer exhibits at least one of acharge injection property and a charge transport property.
 10. The lightemitting element according to claim 1, wherein the base body is formedof a silicon semiconductor substrate on which a transistor is formed andan interlayer insulation layer formed thereon, the first electrode andthe first insulation layer are formed on the interlayer insulationlayer, and the first electrode is connected to the transistor formed onthe silicon semiconductor substrate via a contact hole formed in theinterlayer insulation layer.
 11. A display device in which a pluralityof the light emitting elements according to claim 1 is arranged in atwo-dimensional matrix.
 12. The display device according to claim 11,wherein the first insulation layer, the second insulation layer, thethird insulation layer, the charge injection/transport layer, theorganic layer, and the second electrode are common in the plurality oflight emitting elements.